In the impeller art, and specifically in the art of blower impellers, it is known to rotate an impeller within a housing to generate air flow from the housing in order to perform various functions. For example, in U.S. Pat. No. 4,017,982, the disclosure of which is herein incorporated by reference, an air blower is utilized for providing a high volume of air flow, that may or not be heated, for drying printed circuit boards, often in a somewhat corrosive atmosphere. In instances where corrosive substances might be encountered by a blower, blower components, and the impeller itself, and even more specifically, the vanes of the impeller, may be constructed of various materials that are adapted to withstand corrosive environments. Such materials can be metals such as stainless steel, or can be synthetic materials such as polyvinylchloride.
It is also known that impellers, fans, propellers and the like may be constructed of softer materials, such as rubber, for the purpose of preventing damage to the hand of a user, such as in the case of an open bladed fan, as in U.S. Pat. No. 2,123,146, or in the case of U.S. Pat. No. 2,182,161.
It is additionally known that fan blades can change in shape with rotation as in U.S. Pat. No. 3,759,630 or 4,177,012, or in pitch, as in U.S. Pat. No. 4,187,055. Furthermore, it is known that propellers, blades and the like, can be extended in length, radially outwardly with rotation, by various mechanical mechanisms, such as in U.S. Pat. Nos. 2,079,942 and 3,814,351.